Hydro-climatic Variability and Trend Analysis of Modjo River Watershed, Awash River Basin of Ethiopia

Abstract

Climate change and variability is expected to trigger changes in temperature and precipitation series. This study aimed at assessing variability and trend of hydro-climatic variables at Modjo River watershed. Long-term climate data of 5 representative stations with in the watershed (1981-2010) and streamflow data of Modjo gauging station (1983 -2010) were used. Rainfall variability was analyzed using Coefficient of variation (CV), Precipitation concentration index (PCI) and Standardized anomaly index (SAI). Climate trends were evaluated using Sen’s slope estimator and Mann–Kendall trend test methods. The study revealed Most of the stations showed low variation in annual rainfall (CV% <20) while the main (Kiremt) and short (Belg) season rainfall exhibited CV ranging from low to high. Both annual and seasonal rainfall showed a non-significant trend at all stations for the past 30 years. However, majority of stations showed an increasing trend in annual daily average temperature ranging from 0.2 to 0.6ºC per decade. Following increases in temperature and the subsequent rise in evapotranspiration, streamflow has shown a high significant declining trend. The temporal decline in streamflow at Modjo watershed could likely affect downstream Koka dam water reserve. Thus, any watershed management strategy that can optimize water conservation for sustainable crop production and option that can improve flow to the reserve is vital.

Keywords: Climate change, Climate variability, Hydro-climate, trend, Modjo river watershed

DOI: 10.7176/JEES/11-9-04

Publication date:September 30^th 2021